Typically, in conventional internal combustion engines, the timing between the camshaft and crankshaft is rotationally fixed. More recent engine designs have provided mechanisms to vary this timing in order to maximize fuel economy and minimize harmful emissions emitted from the engine's exhaust.
In order to accomplish this, the overall system must incorporate some type of sensing system to determine the existing phase relationship of the camshaft to the crankshaft, in order to determine the relative change in the phase between the two to maximize fuel economy and minimize harmful emissions. This usually is accomplished with separate sensors on the crankshaft and each independently phase shiftable camshaft, by transmitting these signals to an on-board microprocessor, to generate a phase correction signal. A phase shifting mechanism is activated by the phase correction signal to accomplish the desired result.
Additionally, more engines are designed with sequential fuel injection. The purpose of such an engine design improvement is to increase fuel economy and reduce harmful emissions. This typically is accomplished by configuring a system to sense the rotational position of the camshaft, and by adding a sensor to generate a cylinder identification signal (i.e. engine rotational position). This cylinder identification signal is then sent to an on-board microprocessor, which determines the proper sequential timing of the fuel injection into each cylinder.
Despite these developments, there exists a need to reduce the number of parts or components in such systems, and to reduce the number of process steps being performed, all of which should result in improvements in cost and reliability. In order to reduce the number of sensors needed, and correspondingly to reduce the number of high speed inputs into an on-board microprocessor, a system is needed which can integrate these two functions and yet still perform both the phase shift and the sequential fuel injection functions adequately.